[coreboot] Overclocking Opteron 6200 from coreboot ?

[Timothy Pearson]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On 07/04/2017 07:20 AM, BogDan Vatra wrote:
> Hello,
> 
>   I finally managed to complete my system [0], even that all CPUs
> together are *almost* twice faster than my i7, I want to be change
> *almost* into *more than*, and the only way to do that is to overclock
> my CPUs (or to buy more expensive ones).
> Now the big question is: Is it possible to do it from coreboot? If
> yes, then will the CPU temperature protection still work? E.g. will it
> turn off the computer if the cpu temp will go above 70 degree Celsius?
> If is not possible from coreboot, then, will it be possible to do it
> from Linux? Does anyone has experience on this matter that can share ?
> 
> Thanks,
> BogDan.
> 
> [0]
> CPU: 2x Opteron 6276
> MB: KGPED16
> other uninteresting things.
> 

Yes, it can be done with significant effort (I wrote the software to do
so, which remains unreleased at this time).  That being said, the
Opterons already consume a massive amount of electrical power compared
to the i7.  In my experience if you want to overclock significantly you
need to start dropping CPU load (i.e. unloading cores) to avoid burning
out mainboard circuitry (or PSU wiring!).  The increase in power
consumption versus clock rate is exponential (as you probably know), but
when you start with dual 115W CPUs that can go into some serious power
very quickly.

For reference, I have a 6-core Opteron here (C32) that overclocked to
4.2GHz stably, but it is attached to a massive 5U air cooler and uses
over double its rated TDP in the process.  This was also a hand-picked
HE chip as other chips did not overclock that well.  The power reporting
gives bad numbers under overclock, while the hard thermal limits
continue to function.  Furthermore, overclocking these chips requires
disabling large chunks of the power management functionality, meaning
you'll be using power as if the system is under full load even when it
isn't.

On the balance, I chose not to release the tools due to the significant
liability involved and the fact that (given the AMD-imposed limitations
that had to be hacked around) they not going to help most people do
anything other than burn out hardware and waste power.  Furthermore, I'd
rather see community effort focused on newer architectures (ARM, POWER)
than trying to squeeze a bit more performance / a bit more time from a
terminally non-free architecture (x86).

If you _really_ want to try an overclock anyway, I might be able to
provide the overclocking tools under NDA, but I don't see a cost /
benefit reason to publicly release them at this time ("costs" largely
related to legal liability and such due to the fact that, misused, these
tools will quite happily cause hardware damage).

- -- 
Timothy Pearson
Raptor Engineering
+1 (415) 727-8645 (direct line)
+1 (512) 690-0200 (switchboard)
https://www.raptorengineering.com
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/

iQEcBAEBAgAGBQJZW+QMAAoJEK+E3vEXDOFbNXgH/1QEohu+HlpIlUKUjr0i989b
8caiVaJ0lGphg6gK7bZUfx4Z3DZquWYvseNRuI4F5+db20/Aak2mXQcDbElKoN6q
aF+uD6GRfBXaQs1EYioKKMMcXWjxnyOyJwwUK9rhppGEFINCz+Jgm1gZvO31bO0e
vFkjCt9tZD0ewbA8BxHZqnapvK5hoJCf3VDr1LfJaM2pptwcnZNxn+TyKzun+LIe
BW23c2fGJWG8cWWEoGRR6EL+J3mFEmfHTuJ1DjLcuATMVduLoFo/k4Ru9Aozpc/X
RDFVfEnACQ1pEpyp2h/NV9dPNOD2cqHaqNsMuNpdhBDMXuY5p09KBiZGhyFM86U=
=HEBi
-----END PGP SIGNATURE-----